I have to agree. If your goal is high calorie, high protein trail food in minimum space with minimum weight and with no need to light a fire or even stop moving to eat it, then sure, pemmican and erbswurst and such are old standbys.If your goal is to store fat, why bother making pemmican or erbswurst ? Why not just store the fat on it's own? It gives you a ton more options if you store individual ingredients instead of mixing them.
But if you want fat for the apocalypse, canned meats and rendered fats in can/jars are going to provide many more and much tastier options while lasting even better on the shelf.
If those old-timers had been able to can buffalo instead of drying and powdering it, believe me, most of it wouldn't have ended up jerky or pemmican.
Now as to eggs, great food for many things, not just their fat content.
And olive and purslane are both terrific if they grow in your climate, although you'll need to plan some years ahead to have a good olive grove. If you are in a climate not suitable to olives and avocados or don't have the acreage and lead time, there are annuals like sesame and peanuts in warm areas and many other annual plants/seeds with valuable oils containing essential fatty acids that will grow in a year in many different climates such as hemp, sunflowers, camelina, chia, pumpkin, etc. Many nut trees are also suited to colder climates, although you again have the issue of acreage and lead time with those.
Just as with whole grains versus milled flour, whole seeds will store for longer than their pressed oils, although all fatty/oily foods have relatively short shelf lives compared to other things.